84 SECTIONAL ADDRESSES. 
after all but completing the cocoon, always “remembered” to destroy 
part of its laboriously built home by biting out two deep clefts at one end, 
and how the valve-like door thus made was patiently tested several times 
to make certain of its being of the right size, and then carefully closed 
on the inside with a little soft silk which would not interfere with the 
emergence of the imago.’ In testing the opening the caterpillar extended 
‘half its body out of the cocoon to assure itself that the vent was large 
enough.’ How is it possible to apply any Lamarckian theory of inherited 
experience, or of effort and improvement following from experience, to 
examples like these? The experience of ease or difficulty in emergence 
in the last example, of failure or success in evading enemies in the others, 
will come, not in the stage which made the preparation but in a later 
one, and should it come, the chances of handing on its lessons would be 
negligible. “The prime necessity for an insect, as for all animals which 
cannot in any real sense contend with their foes, is to avoid experience 
of them altogether.’ And the cocoon-making activities described above 
are preparations, made long beforehand, for the avoidance of experience. 
I propose now to refer briefly to some of the objections which have 
been raised against the opinion that Protective and Mimetic Resemblances 
have arisen by Natural Selection, and to consider alternative suggestions. 
Dr. Paul Vignon, in his fine and beautifully illustrated monograph?’ on the 
leaf-like Long-horned Grasshoppers (Tettigoniide) of tropical America, 
comes to the conclusion that the detailed resemblance to decayed leaves 
or leaves apparently mined or eaten by caterpillars, is useless, his reason 
being that other species with the much simpler likeness to uninjured leaves 
are able to hold their own in the struggle with greater success, as shown 
by their comparative abundance. Therefore he considers the details as 
a ‘decoration’ unnecessary in the life of the insect, agreeing with 
Brunner’s theory of ‘ Hypertely.’* I believe, on the contrary, that the 
°6 The arguments in this paragraph were brought forward in the unpublished 
discussion * Are Acquired Characters Hereditary?’ at the Manchester Meeting, 
September 5, 1887 (Report, p. 755). The later occasions on which they were developed 
and recorded are mentioned on p. 155, n. 1, of Essays on Evolution, where they are 
reprinted (pp. 117, 118, 154-160). 
* Arch. du Mus., 6, V, p. 57, 1931. See also his Introduction & la Biologie 
xpérimentale. Les étres organisés. Activités, instincts, structures. Encyclopédie 
Biologique, VIII, Paris, 1930. 
* Prof. J.M. Baldwin has kindly written the following note on a subject (recalled 
by Dr. Vignon’s memoir) we had discussed together :—- 
“The continued lack of enthusiasm for Natural Selection in France seems at first 
glance remarkable. It seems inconsistent with the French love of logical “‘ clearness 
and distinctness ”’ given as the criteria of truth by the French philosopher Descartes, 
for whom his countrymen have the greatest veneration. But the tendencies shown 
in the work of Delage and Giard in the last generation appear still in the publications 
of such thinkers as Le Roy and Brunschweig. Naturally I take no account of special 
researches of younger biologists with which I am not familiar. The philosophical 
writers, at least, retain a diluted Lamarckism, somewhat hesitant, it is true, and 
always on the defensive. It is part of the vitalism expressed by Bergson in the terms 
“élan vital’ and “ évolution créatrice.’”” The Positivism of Auguste Comte is still 
completely demoded, except in the sociological work of Durkheim and Lévy Bruhl, 
in which the question of the method of biological evolution has no place. The revolt 
against Bergsonian vitalism in the intellectual world has been directed against its 
mysticism, but has not extended itself to questions of biology.’ 
